1. Field Of The Invention
The present invention is directed to an electronic illumination apparatus. Specifically, the present invention is directed to an improved motor driven electronic illumination apparatus having rotational operation for use in, for example, audio equipment which is capable of indicating the operational position of its knob by means of light from a built-in light source, for example, an LED (Light Emitting Diode).
2. Description Of The Prior Art
In the prior art it is known to produce motor-driven electronic illumination apparatus comprising a variable resistor of rotational operation. This illumination apparatus is exemplified by FIGS. 5-8.
As shown in FIG. 5, prior art electronic illumination apparatus have comprised a variable resistor 1, a speed reduction gear mechanism 2, and a motor 3. The variable resistor 1 is composed of a metal bushing 5, a resistance varying means, and an illuminating means 16. The bushing 5 has a housing member 4.
The resistance varying means is composed of a rotational operation shaft 11, which is supported by the bushing 5 and freely rotatable, a driver 12, a brush holder 13, a brush 14, and a resistor substrate 15. The rotational operation shaft 11 is integrally formed of a cylindrical portion 7 which has a through-hole 6 therein, a flange 8 disposed on the rear end of said cylindrical portion 7, a projection 9 disposed at a position on the periphery of said flange 8, and a bow-shaped linkage 10 disposed on the end of said projection 9. The brush holder 13 is linked with the bow-shaped linkage 10 by means of a projection 12A extending from the driver 12. The resistor substrate 15 is held by a substrate holder 19, and a resistor is formed on the surface of said resistor substrate 15. In the prior art, the rotational operation shaft 11, the flange 8, and the bow-shaped linkage 10 have been made of metal, generally from a die-cast mold.
The illuminating means is comprised of a light emitting diode ("LED"), 16 which serves as a light source and is located inside the housing member 4 and at the rear end of the feed-through hole 6 of the rotational operation shaft 11, and a holder 17 for holding the LED 16.
Rotational motion of the rotational operation shaft 11 is restricted because upon rotation the projection 9 of the rotational operation shaft 11 contacts a projection 18 disposed at the lower portion of the concaved portion of the housing 4 of the bushing 5.
The speed reduction gear mechanism 2 comprises a housing box 20. The motor 3 connects to the housing box 20 and has a drive means, a shaft 3A, which projects into the speed reduction gear mechanism 2. The back of the bushing 5, at the substrate holder 19 of the variable resistor 1, contacts the housing box 20 to make an integral body by means of a U shaped bracket 21, to which the motor 3 is fastened by screws.
This structure makes it possible to transmit the rotational motion of the motor 3 to the driver 12 of the variable resistor 1 through the speed reduction gear mechanism 2.
During operation of the motor 3, the rotational motion thereof is reduced in its speed by the speed reduction gear mechanism 2 and transmitted to the driver 12 of the variable resistor 1. The brush holder 13 linked with projection 12A is rotated so that the brush 14 held by the brush holder 13 slides over the resistor substrate 15 thus changing resistance values.
Concurrently, voltage is applied across terminals 22 and the LED 16 is activated to emit light. The emitted light is directed through the through-hole 6 of the rotational operation shaft 11 to illuminate an indicator knob mounted on the end of the rotational operation shaft 11.
The transmission of rotational motion between a last stage reduction gear 23 of the speed-reduction gear mechanism 2 and the projection 12A of the driver 12 is controlled by means of a friction clutch 25 which comprises a sheet spring 24. The friction clutch 25 allows the variable resistor 1 to be manipulated by rotating the rotational operation shaft 11 by hand without turning the motor because the clutch 25 will slip.
While this prior art illumination apparatus provides important advantages by providing rotational operation with variable resistance, it has the disadvantage that the cylindrical portion 7 having the feed-through hole 6, the flange 8 on the rear end of the cylinder, the projection 9 on the periphery of the cylinder, and the bow-shaped linkage 10 on the rear end of the cylinder must be built in an integral fashion to form the rotational operation shaft 11. Complex molding techniques are thus required, such as metal die casting or the like which require complicated molding die, to manufacture the rotational operation shaft 11.
As a result, the electronic illuminating apparatus comprising the aforementioned structure has the disadvantage of requiring that a new mold or die be manufactured when changes in production specifications for the length of the rotational operation shaft 11, the diameter of the knob mounting portion 11A of the rotational operation shaft 11, or the position of the flat portion 11B of the rotational operation shaft 11 are desired.
Another disadvantage of the prior art apparatus is that the flange 8 is integrally molded with the rear end of the rotational operation shaft 11 but has a larger diameter than the fitting receptacle of the bushing 5. Thus, the rotational operation shaft 11 must be inserted from the rearward end of the receptacle of the bushing 5 during assembly. When a strong rearward thrusting force is applied to the rotational operation shaft 11 from the frontward end at the time of mounting a knob onto the rotational operation shaft 11, a danger exists of inflicting damage the internal component parts of the apparatus, for example, the resistor substrate 15.
Another disadvantage of the prior art apparatus is that it has a stopper mechanism to restrict the extent of rotational motion of the rotational operation shaft 11 which is built in such a way that the projection 9 of the rotational operation shaft 11 hits the projection 18 of the concaved housing 4 of the bushing 5 producing an impact which can adversely effect use of the apparatus in audio equipment. This is particularly true when the rotational operation shaft 11 and the bushing 5 are made of metal, causing a sound which may result in annoying effects imposed on certain electrical parts, especially those intended for use in audio equipment.
Another disadvantage of the prior art apparatus is that the long and slender feed-through hole 6 which serves as the light channel for the light emitting source of the LED 16 causes the light intensity at the indicator knob to be adversely diminished, even when an LED of strong directivity is used. Similarly, a problem exists in that scattering of illumination intensity occurs.
Thus, none of the prior art apparatus address the problems of the need to prepare a new die cast mold each time the product specification is changed, the danger of damaging the internal components of the apparatus due to thrust in the rearward direction on the rotational operational shaft, or the inadequacy of the light reaching the indicator knob from the illumination source.